Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

164
FXUS63 KLOT 182002
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
302 PM CDT Thu Jun 18 2026

.KEY MESSAGES...

- An axis of showers may drift across the area Friday evening
  through early Saturday AM (30-40% chance) with isolated
  embedded non-severe storms possible (20% chance).

- A period of heavy rain with embedded thunderstorms is expected
  Sunday which may lead to flooding.

&&

.DISCUSSION...
Issued at 302 PM CDT Thu Jun 18 2026

Northwesterly flow across the area in the wake of yesterday`s
strong weather system paired with decent coverage of diurnal
cumulus has helped keep temperatures cooler today with
temperatures in the low to mid 70s across the area. A lake
breeze hugging the lakeshore into Cook County and well inland
across northwest Indiana have held temperatures in the 60s
there. Meanwhile, a few light showers have developed into
portions of southeast Minnesota associated with a weak wave
diving across the Upper Midwest. This may try to sneak in a few
light showers or sprinkles into far northern/northwest Illinois
this evening but have held off on a formal mention in the
gridded forecast with this update given weak forcing amidst an
overall dry airmass.

While winds will remain generally out of the west to northwest
into Friday (away from the lakeshore), lower cloud coverage
should help temperatures warm into the mid-upper 70s across the
area. A weak lake breeze may cool temperatures back into the
upper 60s/lower 70s near the lakeshore in the afternoon. Heading
into the evening hours, a shortwave is forecast to dive
southeast within the broader upper level northwest flow. This
feature may lead to shower and thunderstorm development across
portions of Minnesota and Wisconsin during the day on Friday.
This activity may drift into northern Illinois in a decaying
mode. Some hi-res guidance maintains showers and possible
isolated embedded thunderstorms along an elevated fgen axis
that slides south across the area through the night into early
Saturday morning. Any lingering showers should come to an end
by late morning south of I-80 with temperatures warming into the
upper 70s to lower 80s.

A compact system is expected to eject off the Rockies and move
east across the Central Plains late Saturday into Sunday
bringing a period of inclement weather to the region on Sunday.
There remains model variability in the handling of the
associated surface low, including its strength and exact track,
which will influence which areas are most favored to experience
a longer duration of heavy rainfall and any possible severe
thunderstorm and flooding threats. More northerly solutions
(NAM/ECMWF) would support heavy rainfall across nearly the
entire area, whereas the more southerly solutions (GFS/UKMET),
focus the heavy rain axis south of I-80. The varying solution
tracks may be tied to differences in handling any influence from
an expanding Canadian surface high and the position of closed
mid-upper lows meandering around the southern Hudson Bay/Ontario
region. All in all, Sunday continues to be a day to monitor,
particularly for any flooding concerns (currently a level 1 and
2 out of 4 threat for the local area). If a more northern track
verifies this could lift a marginal severe weather threat north
into portions of the area, mainly south of I-80.

Beyond Sunday we enter a brief dry period as the aforementioned
high pressure expands into the area in the wake of the
departing surface low. Onshore winds will likely keep
temperatures cooler than normal to start the week with highs in
the lower to mid 70s (typically lower 80s in mid-late June).
Temperatures then gradually warm through midweek into the upper
70s, with our next chance of rain returning during the Tuesday
night into Wednesday timeframe as another system dives southeast
within the broader northwest flow pattern.

Petr

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1217 PM CDT Thu Jun 18 2026

There are no key concerns to highlight for the 18Z TAF period.

Expect WNW winds near or above 10 kt gusting occasionally to
near 20 kt through the afternoon, subsiding to below 10 kt this
evening. WNW 10 to 15 kt during the daytime Friday. VFR can be
expected through the period.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Beach Hazards Statement until 3 PM CDT this afternoon for
     INZ002.

LM...None.

&&

$$

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